Operation pedal devices for a vehicle used when a driver operates a vehicle include a parking brake device, a brake pedal device, an accelerator pedal device, a clutch pedal device and the like. This type of operation pedal devices for a vehicle include one provided with a pedal arm rotatably provided on a vehicle body and a pedal pad attached to a pad mounting portion provided at a tip end portion of the pedal arm as an operation pedal operated by the foot of the driver. Moreover, the operation pedal includes one in which the pedal pad made of an elastic member is fitted in the pad mounting portion provided with an engaging portion so that the pedal pad does not remove from the pad mounting portion by a stepping-on operation on the pedal pad by the driver (refer to Japanese Laid-Open Patent Application No. 2012-208784 and No. 2011-215869, for instance), for example. The pad mounting portion disclosed in the aforementioned patent application is formed such that a flat plate-shaped steel plate is bent by pressing and two flat plates are faced with each other, and the foot of the driver is placed on one of the two flat plates. The pad mounting portion has an engaging portion provided on a side surface portion connecting the two flat plates and is mounted by engaging an engaged portion of the pedal pad with this engaging portion.